Acoustic device



P. M. RAINEIY.

ACOUSTIC DEV-ICE. APPLICATION FILED 056.27; 1918.

Patenwd Mar. 29, 1921.1

2 SHEETS-SHEET 1.

/n ven-fo'r: Pau/ M Rd/hey P. M. R'AINEY.

ACOUSTIC DEVICE.

APPLICATION FILED 0Ec.27. i918.

1,37 3,01 9. I Patented Mar. 29,1921.

2 SHEETS-SHEET 2- m vemor: Pau/ M fia/ney UNIT-ED, sTATEs PATENT OFFICE.

PAUL I. RAINEY, OF GLEN RIDGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, IN GQRPORATED, OF NEW YORK, N. Y.', A CORPORATION OF NEW YORK.

ACOUSTIC DEVICE.

Specification of Letters Patent.

Application filed December 27, 1918. Serial No. 268,505.

To all whom it may concern e it known that I, PAUL M. RAINEY, a citizen of the United States, residin at Glen Ridge, in the\. county of Essex, tate of New Jersey, have invented certain new and useful Improvements in Acoustic De-;

vices, of which the following is a full, clear, concise, and exact description.

This invention relates to acoustic devices,

and more particularly to a means for inamplitude of vibration in response to these small forces.

It is, therefore, the object of the presentinventionv to provide an acoustic device in which the vibratingsystem is so arranged that a maximum movement of the diaphragm results from the small forces acting upon it. A further object is to provide an acoustic device in which a very sensitive diaphragm is employed, and damping means are also included-to overcome the disturbing effect due to the diaphragm vibrating in accordance with its own natural frequency.

To attain these objects and in accordance with a feature of this invention, there is provided an acoustic device in which a chamber is located on one side of the diaphragm, and

a vacuum or exhaust pump is applied to this chamber in such a manner as to cause a flow of air through an orifice into this chamber, this flow of air being restricted by the movement' of the diaphragm. This and other 1 and 2, there is disclosed a telephone transmitter of the well-known type modified to include the features of the present invention. The front plate 4 equipped with a mouthp1ece5 is secured o the common type of casing 6, this casin being provided with a mounting lug 7. Secured to the front plate 4 by means of the screws 88, passing through the holes 9-9, is the cup-shaped bridge member l0, the central portion of which is provided with an opening to receive the thimble 11. This thimble is held in place by'means of the nut 12 and is insulated from the brid e member 10 by means of the insulating was ers 13 13. The stem 14 of the transmitter button passes through the opening in the thimble l3 and is held in place, after being suitably adjusted, by means of the screw 15. The front stem 16 of the transmitter button rests against the diaphragm 17 which bears against the back portion of plate 4, but is insulated therefrom by means of the washer 18 of oiled linen or other suitable material. The front stem 16 is held against the diaphragm with the Patented Mar. 29, 1921.

proper tension by means of the, damping spring 19 which is secured to the bridge member by means of the screws 20-20 and the plate 21. These parts, however, are insulated from the bridge by means of the insulators 22 and 23 which are preferably 'of mica.- Secured to the bridge member 10 by means of screws 24, which pass through openings 2525, is a second cup-shaped member 26 equipped with a central opening through which the stem 16 of the transmitter button extends. The casing 6 is provided with an opening 27 somewhat larger than the diameter of a tube 28 which extends therethrough and is threaded into the bridge member 10. A number of perforations 29 are provided in the bridge member 10 to permit free access of air. The tube 28 is connected to a vacuum chamber or a suction Pu p In the operation of this device, as sound waves impinge upon the diaphragm 17, causing it to move inwardly, the space between the member 26 and the diaphragm 17 is decreased, the current of air flowing through this space is further restricted, and the suction force acting upon the diaphragm correspondingly increased. This current of air flows throug the openings 27 and 29, and thence through the restricted space between the diaphragm 17 and the member 26, through the central opening in the member 26 and out through the tube 28in the direction indicated by the arrows. The amplitude of vibration is therefore considerably increased by the resulting suction acting upon the diaphragm. In the return movement as the diaphragm moves outwardly, the area of the restricted space is increased, thereby facilitating the movement. Moreover, the thin layer of air existing betweenthe diaphragm and the member 26 also acts in conjunction with spring member 19 to provide suitable damping for the moving system.

In the construction shown in Figs. 3 and 4, the same principle of operation is employed. The cup shaped casing 30 is provided with a tube 31 threaded therein and connected 'to a suitable vacuum chamber or suction pump 39. A vent 32 is provided in the casing 30 to allow the entrance of air back of the diaphragm 33. In close face to face relation with the diaphragm 33 is the plate member 34 which is secured to the casing by means of the screws 35- 35. This member is provided with openings 36-36 of suflicient size to allow the entrance therethrough of the 'core members 37-37' and .tion, the movement of the diaphragm is still further increased. As this current ceases to flow in electromagnet 38, the diaphragm 33 is free to return toitsnormal positlon, but the return movement is dam ed to a (561173.111 extent by the retarding e ect I which results from the suction of airthrough the restricted section- However, as the diaphragm moves outwardly, this restricted space becomes larger and the retarding ef-' fect becomes less and less, permitting the diaphragm to return to its normal position.

What is claimed is: 1. An acoustic device comprising a diaphragm to be set in vibration, and means cooperating with a current of air for increasing the amplitude of vibration of said diaphragm.

2. An acoustic device comprising a dia phragm to be set in vibration, and a damping plate in close face to face relation thereto, said diaphragm and plate coiiperating to increase the amplitude of vibration of the diaphragm by controlling the flow of a ourrent of air between the diaphragm andthe damping plate.

3. An acoustic device comprising a diaphragm to be set in vibration, a damping a' chamber at the rear of said dampin plate, and means for causlng a current 0 a1r at less than atmospheric pressure to flow be-- tween the diaphragm and said damping plate into said chamber.

4. An acoustic device comprising a diaphragm to be-set in vibration, and a damping plate in close face to face relation thereto, said diaphragm and plate cooperating with .a current of air controlled by the plate in close face to face relation thereto,

movement of the diaphragm to increase its amplitude of vibration.

5, An acoustic device comprising a casing, a diaphragm forming an end-wall for said casing, a damping plate mounted in close. face to face relation to said diaphragm and having a central opening therein, and means for causing a'currentof air at less than atmospheric pressure to flow radially between said diaphragm and damping plate.

In witnesswhereof, I hereunto subscribe my name this 24th day of December, A. D., 1918. v.

PAUL M. RAINEY. 

